The present application claims priority to Japanese Application(s) No(s). P2001-187229 filed Jun. 20, 2001, and P2001-197067 filed Jun. 28, 2001, which application(s) is/are incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a cleaning tape for cleaning a surface of a magnetic head, particularly a magnetoresistive type head, used in a tape-type magnetic recording system, and a surface of a tape path.
2. Description of the Related Art
In the field of video tape recorders (VTR) etc., a higher recording density has become demanded for improving picture quality. The deterioration of the picture quality caused by accumulation of deposits on the sliding surface of a head, however, becomes greater along with an increase in the recording density. Therefore, cleaning tapes with a sufficient cleaning effect have become demanded.
In digital magnetic recording systems, on the other hand, magnetoresistive (MR) heads, giant magnetoresistive (GMR) heads, etc. are now being employed for realizing higher recording density. However, a magnetoresistive element such as an MR head, GMR head, or a tunnel connection-magnetoresistive (TMR) head is more vulnerable to electrostatic discharge damage compared to a conventional so-called inductive type head. Therefore, the electric resistivity of the surface sliding with the head must be kept to 1xc3x97106 xcexa9/inch2 or less.
Also, the magnetoresistivity of an MR head, GMR head, or other magnetoresistive head changes when the thickness of the effective surface of the head, that is, the xe2x80x9cdepthxe2x80x9d, changes. Due to this, the output power of the playback signal is influenced. Therefore, it is necessary to reduce head wear as much as possible.
As described above, in a digital recording system using a magnetoresistive type head, a cleaning tape having an electric resistivity of its magnetic surface of not more than 1xc3x97106 xcexa9/inch2, a low head abrasion, and a high cleaning effect has been required. However, up to now, a cleaning tape like this has not been realized by a general production technique of a coating (metal particulate) type magnetic recording medium.
Japanese Unexamined Patent Publication (Kokai) No. 8-315327 discloses a cleaning tape having a magnetic layer serving as a cleaning layer formed by metal evaporation. If forming the magnetic layer by metal evaporation, the magnetic layer does not contain any non-conductive binder or additive. Therefore, it becomes possible to lower the electric resistivity of the tape path surface.
However, when using the cleaning tape described in Japanese Unexamined Patent Publication (Kokai) No. 8-315327 for cleaning a magnetoresistive type head, the polishing power is too high and therefore the head abrasion could not be kept within an acceptable range.
Summarizing the problems to be solved by the invention, recently, there has been growing demand for improving picture quality. The electromagnetic conversion characteristics of magnetic recording media have been improved, and digital VTR systems employing narrow tapes having a width of 8 mm or less have been proposed. Also, in recording media for computers, tapes having a width of xc2xd inch or less have been proposed for recording and reproduction at a higher density.
At the present time, in order to secure sufficient electromagnetic conversion characteristics even with such narrow-width tape, thin film type magnetic recording media like metal evaporated tape have to be used. However, when increasing the recording density, the wavelength is shortened and the tracks are narrowed, so deposits on the head sliding surface have a greater effect on the electromagnetic conversion characteristics compared with a conventionally utilized system. Therefore, for a general user, a cleaning tape becomes a necessity when considering the maintenance of the set.
As described above, since a magnetoresistive type head has a lower resistance to electrostatic discharge damage compared to an inductive type head, unless the electric resistivity of the sliding surface is made 1xc3x97106 xcexa9/inch2 or less, the head element is damaged by electrostatic discharge.
Also, a magnetoresistive element obtains output power from resistivity. If the head is abraded, the resistivity changes. The playback output waveform will then become larger compared to before abrasion. If the resistivity changes more than an allowable extent, the adjustment point of the pre-adjusted head amplifier will shift and the playback waveform will become nonlinear.
To obtain a metal evaporated type cleaning tape having a sufficiently low electric resistivity of the surface sliding with the head, featuring small head abrasion, and having a sufficient cleaning effect, it is necessary to suitably control the size and density of projections on the tape surface as described in Japanese Unexamined Patent Publication (Kokai) No. 8-315327. However, up to now, the size and density of surface projections and the thickness of the magnetic layer as required for cleaning of a magnetoresistive type head have not been sufficiently investigated.
An object of the present invention is to provide a cleaning tape having a low electric resistivity, a low head abrasion, and a sufficient cleaning effect, more particularly a cleaning tape suitable for cleaning a magnetoresistive type head.
According to the present invention, there is provided a cleaning tape comprising a nonmagnetic base film, an evaporated metal layer formed on the nonmagnetic base film, and an inorganic protective film formed on the evaporated metal layer.
Preferably, the evaporated metal layer is an alloy magnetic layer mainly composed of cobalt, and the thickness of the alloy magnetic layer is about 30 nm or more.
Preferably, the cleaning tape further comprises surface projections formed on the nonmagnetic base film by particles having a diameter of 35xc2x15 nm and a density of about 300xc3x97104 to 1500xc3x97104 particles/mm2.
Alternatively, the cleaning tape further comprises surface projections formed on the nonmagnetic base film by particles having a diameter of 25xc2x15 nm and a density of about 500xc3x97104 to 2000xc3x97104 particles/mm2.
Alternatively, the cleaning tape further comprises surface projections formed on the nonmagnetic base film by particles having a diameter of 15xc2x15 nm and a density of about 500xc3x97104 to 4000xc3x97104 particles/mm2.
Preferably, the evaporated metal layer is an electroconductive layer. More preferably, the electroconductive layer comprises a nonmagnetic layer.
Preferably, the cleaning tape further comprises surface projections formed on the nonmagnetic base film by particles having a diameter of 25xc2x15 nm and a density of about 500xc3x97104 to 2000xc3x97104 particles/mm2.
Preferably, the electroconductive layer is a metal layer or alloy layer comprising at least one of aluminum or copper. In that case, the thickness of the electroconductive layer is about 20 nm or more.
Alternatively, the electroconductive layer is a metal layer or alloy layer comprising at least one of tungsten, molybdenum, magnesium, iron, and nickel. In that case, the thickness of the electroconductive layer is about 30 nm or more.
Preferably, the inorganic protective film comprises a carbon protective film. Preferably, the thickness of the inorganic protective film is about 3 nm to 50 nm.
Due to this, it becomes possible to lower the electric resistivity of the surface of the cleaning tape, reflect the size and density of the particles on the nonmagnetic base film on the cleaning tape surface, and control the head abrasion and cleaning effect to the optimal ranges.